Fostex FE-108 Σ
FE-108 Σ is the smallest model of the legendary Sigma series. Unlike the bigger models it has half-roll surround and a dust cap instead of a whizzer cone.
This is the manufacturer's brochure
My Measurements
Driver Properties | Thiele - Small Parameters | ||||
---|---|---|---|---|---|
Chassis material | Vacuum Molded Aluminum Alloy | Parameter | Measured | Datasheet | |
Membrane material | Banana Pulp Paper | Fs | 70.5Hz | 80 Hz | |
Magnet System | Ferrite | Re | 6.5 Ω | 6.5 Ω | |
Surround | Cloth | Qms | 2.10 | 2.21 | |
Voice Coil Diameter | 26 mm | Qes | 0.21 | 0.22 | |
Nominal Impedance | 8 Ω | Qts | 0.19 | 0.20 | |
Sensitivity | 92 dB/W/m | Vas | 10.3 ltr | 7.07 ltr | |
Rated Power | 5W | Le | 0.25 mH | N/A |
![SPL Responce of Fostex FE-108 Sigma at 1m on axis and 15 30 deg off axis](images/Fostex_FE_108_Sigma_0_15_30.png)
Frequency response at 1m with 2.83 V input RED - on axis, BLUE - 15 º off axis, GREEN - 30 º off axis
![Second, Third and Fourth Harmonic of Fostex FE-108 Sigma in 18 ltr sealed box](images/Fostex_FE_108_Sigma_THD.png)
The second, third and fourth harmonic curves measured at 2.83V input RMS.
![Burst decay Responce of Fostex FE-108 Sigma at 1m in 18 ltr sealed box](images/Fostex_FE_108_Sigma_BD.png)
Burst decay response, measured at 1m on axis
![The impedance of Fostex FE-108 Sigma in 18 ltr seled box](images/Fostex_FE_108_Sigma_Z.png)
The impedance curve in 18 ltr sealed box
Conclusion
This driver has a typical T/S parameters for a backloaded horn applications. It keeps the excellent sound signature of the Sigma series with surprising solid sound performance for its dimensions.